Recent developments in dense geodetic observation of volcanoes have enabled us to handle data in real-time. Monitoring agencies detect volcano unrest using numerous instruments and quickly broadcast volcanic activity alerts but based on little quantitative information. Residents on volcanoes seek predictive, practical, and reliable alerts including place, time, and magnitude directly linked to disaster mitigation activities. A strategy I proposed in this study answers the question of the magnitude of a foreseen eruption. Far-field displacements by geodetic instruments provide the signals of deflating magma reservoirs, and may give predictive maximum magnitude Mvp of a looming eruption. This may play an important role in antidisaster measures because it is the parameter most determinate for evacuation. Continuous monitoring of Mvp may also yield valuable information for judging the termination of an eruption because its stagnation indicates magma feeding disconnection from reservoir to shallower part. I believe that predictive volcanic early warnings with quantitative Mvp can provide truly effective, practical information to residents and local governments potentially affected by active volcanoes.
Keywords: volcano eruption, eruption magnitude, volcanic early warning, disaster operation, real-time analysis